To keep pace with the demands in optical communications, electro-optic modulators should feature large bandwidths, operate across all telecommunication windows, offer a small footprint, and allow for CMOS-compatible fabrication to keep costs low(1). Here, we demonstrate a new ultra-compact plasmonic phase modulator based on the Pockels effect in a nonlinear polymer. The device has a length of only 29 mu m and operates at 40 Gbit s(-1). Its modulation frequency response is flat up to 65 GHz and beyond. The modulator has been tested to work across a 120-nm-wide wavelength range centred at 1,550 nm, and is expected to work beyond this range. Its operation has been verified for temperatures up to 85 degrees C and it is easy to fabricate. To the best of our knowledge, this is the most compact high-speed phase modulator demonstrated to date

Electro-optic modulation at frequencies of 100 GHz and beyond is important for photonic-electronic signal processing at the highest speeds. To date, however, only a small number of devices exist that can operate up to this frequency. In this study, we demonstrate that this frequency range can be addressed by nanophotonic, silicon-based modulators. We exploit the ultrafast Pockels effect by using the silicon-organic hybrid (SOH) platform, which combines highly nonlinear organic molecules with silicon waveguides. Until now, the bandwidth of these devices was limited by the losses of the radiofrequency (RF) signal and the RC (resistor-capacitor) time constant of the silicon structure. The RF losses are overcome by using a device as short as 500 mm, and the RC time constant is decreased by using a highly conductive electron accumulation layer and an improved gate insulator. Using this method, we demonstrate for the first time an integrated silicon modulator with a 3dB bandwidth at an operating frequency beyond 100 GHz. Our results clearly indicate that the RC time constant is not a fundamental speed limitation of SOH devices at these frequencies. Our device has a voltage-length product of only V p L511 V mm, which compares favorably with the best silicon-photonic modulators available today. Using cladding materials with stronger nonlinearities, the voltage-length product is expected to improve by more than an order of magnitude. Keywords: 100GHz; high-speed silicon modulator; nanophotonics; silicon-organic hybrid INTRODUCTION High-bandwidth electro-optic modulators are key components for a variety of applications such as photonic transceivers for long-haul and on-chip communications, 1 radio-over-fiber links, low-noise microwave oscillators 2 and optical frequency comb generation. 3 However, achieving a small footprint, low power consumption, low modulation voltage and high-speed operation 4,5 remains a challenge. Because unstrained silicon does not possess a x (2) -nonlinearity, 6 state-of-the art silicon photonic modulators mainly rely on free-carrier dispersion (a plasma effect) in pin or pn junctions. [7][8][9] Reversed-biased pn junctions are intrinsically faster than forward-biased pin diodes 7 and already enable 50 Gbit s 21 on-off keying with a voltage-length product of V p L528 V mm.10 Unfortunately, such plasma-effect phase modulators produce undesired intensity modulation as well, and they respond nonlinearly to the applied voltage.An alternative approach uses hybrid integration of III-V epitaxy stacks grown on InP substrates, which are subsequently transferred to silicon-on-insulator waveguides to create high-speed electro-absorption modulators.11 Recently, such a device demonstrated a 3-dB bandwidth greater than 67 GHz, representing the fastest modulator realized on a silicon chip to date. Advanced modulation formats such as quadrature amplitude modulation, however, require phase modulators with a linear response and a pure phase modulation, rendering the electro-optic effect (Pockels effect 12 ) partic...

CMOS-compatible optical modulators are key components for future silicon-based photonic transceivers. However, achieving low modulation voltage and high speed operation still remains a challenge. As a possible solution, the silicon-organic hybrid (SOH) platform has been proposed. In the SOH approach the optical signal is guided by a silicon waveguide while the electro-optic effect is provided by an organic cladding with a high χ (2) -nonlinearity. In these modulators the optical nonlinear region needs to be connected to the modulating electrical source. This requires electrodes, which are both optically transparent and electrically highly conductive. To this end we introduce a highly conductive electron accumulation layer which is induced by an external DC "gate" voltage. As opposed to doping, the electron mobility is not impaired by impurity scattering. This way we demonstrate for the first time data encoding with an SOH electro-optic modulator. Using a first-generation device at a datarate of 42.7 Gbit/s, widely open eye diagrams were recorded. The measured frequency response suggests that significantly larger data rates are feasible. Raj, R. Ho, J. E. Cunningham, and A. V. Krishnamoorthy, "Ultra-low-energy all-CMOS modulator integrated with driver," Opt. Express 18(3), 3059-3070 (2010). 33. S. S. Li, and W. R. Thurber, "Dopant density and temperature-dependence of electron-mobility and resistivity in n-type silicon," Solid-State Electron. ©2011 Optical Society of America

Organic materials combined with strongly guiding silicon waveguides open the route to highly efficient electro-optical devices. Modulators based on the so-called silicon-organic hybrid (SOH) platform have only recently shown frequency responses up to 100 GHz, high-speed operation beyond 112 Gbit/s with fJ/bit power consumption. In this paper, we review the SOH platform and discuss important devices such as Mach-Zehnder and IQmodulators based on the linear electro-optic effect. We further show liquid-crystal phase-shifters with a voltage-length product as low as V π L = 0.06 V·mm and sub-μW power consumption as required for slow optical switching or tuning optical filters and devices.

Advanced modulation formats call for suitable IQ modulators. Using the silicon-on-insulator (SOI) platform we exploit the linear electrooptic effect by functionalizing a photonic integrated circuit with an organic χ (2) -nonlinear cladding. We demonstrate that this silicon-organic hybrid (SOH) technology allows the fabrication of IQ modulators for generating 16QAM signals with data rates up to 112 Gbit/s. To the best of our knowledge, this is the highest single-polarization data rate achieved so far with a silicon-integrated modulator. We found an energy consumption of 640 fJ/bit.